The present invention relates to sewing machines generally, and more particularly to the pattern control mechanisms of sewing machines which control the motion of the stitching needle and the material for the purpose of generating stitch patterns ranging from simple zig-zag patterns to complex ornamental patterns.
To provide different stitch pattern functions, commercially available sewing machines have relatively complex arrangements of cams, linkages, levels and cranks to reciprocate and oscillate the machine's needle bar, and to control the movement of the material feed dog found beneath the needle plate in the base of the machine. A purchaser of a sewing machine will normally chose a machine which meets his or her experience level and needs: a beginner sewer will likely choose a simple straight stitch machine with only straight stitch capability; a sewer with some experience may wish to purchase the additional versatility found in a simple zig-zag machine while more advanced sewers would likely want to expand to more complex commercially available machines with complex stitch width and stitch length control as provided by, for example, pattern selector knobs and/or drop in pattern discs. To upgrade equipment a sewer will normally have to buy a new machine, since the construction and complexity of most sewing machines economically preclude taking, for example, a straight stitch machine and upgrading it to a more complex ornamental pattern stitch machine.
It is a primary object of the present invention to provide a sewing machine which is greatly simplified in construction as compared to conventional equipment and which is upgradable from a straight stitch machine to a machine capable of handling very complex pattern stitches. Still other objects of the invention will become apparent from the following specification and claims.